With advances in recombinant DNA technology, techniques to obtain objective gene products have developed through expression of a foreign gene in hosts such as bacteria, fungi, animals, plants, and insects, and proliferation of the transformants. For example, culture of recombinant yeasts allows production of large amounts of objective gene products by means of fermentative production. Concerning the production of valuable organic acids such as L-lactic acid, there have been many reports of the L-lactic acid production experiments by introducing the L-lactate dehydrogenase gene into yeast Saccharomyces cerevisiae. 
To achieve high productivity of the objective substance from recombinants, a stable high-level gene expression system must be established. The inventors have already established a system to express an L-lactate dehydrogenase gene using an original promoter function of the foreign PDC1 gene and exclude the expression of PDC1 protein that is expressed by the original foreign promoter, by linking the objective valuable gene (L-lactate dehydrogenase gene in this case) in the downstream of chromosomal PDC1 promoter and disrupting the yeast chromosomal PDC1 gene simultaneously. The inventors have disclosed in Japanese Published Unexamined Patent Application 2003-164295 that the use of this system overcomes conventional difficulties and allows stable high-level gene expression.
Although such a stable high-level gene expression system has been established, a promoter with strong expression potency is needed to further increase the productivity of recombinant products. The yeast promoters published include alcohol dehydrogenase 1 gene (ADH1) promoter (J Ferment Bioeng, 1998, Vol. 8 6(3) pp 284-289), triose phosphate isomerase gene (TPI1) promoter (FEMS Microbial Lett, 1999, Feb. Vol. 171 (2) pp 133-140), and the like.